1. Field of the Invention
The present invention relates to a barrier laminate, especially to a barrier laminate excellent in producibility and having a low water vapor permeability, and further to a barrier film substrate, a device and an optical component comprising the barrier laminate.
2. Description of the Related Art
Heretofore, a barrier film fabricated by forming a thin metal oxide film of aluminum oxide, magnesium oxide, silicon oxide or the like on the surface of a plastic film is widely used for wrapping or packaging articles that require shielding from various gases such as water vapor or oxygen and for wrapping or packaging edibles, industrial articles and medicines for preventing them from being deteriorated.
Recently, in the field of liquid-crystal display devices and organic EL devices, plastic film substrates are being used in place of glass substrates that are heavy and readily cracked or broken. As applicable to a roll-to-roll system, plastic film substrates are advantageous in point of cost. However, plastic film substrates are problematic in that their water vapor-barrier capability is not good as compared with that of glass substrates. Therefore, when a plastic film substrate is used in a liquid-crystal display device, then water vapor may penetrate into the liquid-crystal cell, thereby causing display failures.
For solving the problem, it is known to use a barrier film substrate produced by forming a water vapor barrier layer on a plastic film. As such a barrier film substrate, known are one produced by depositing silicon oxide on a plastic film in a mode of vapor deposition (e.g., see JP-B 53-12953 (pp. 1-3)), and one produced by depositing aluminum oxide thereon (e.g., see JP-A 58-217344 (pp. 1-4)); and their barrier capability is on a level of 1 g/m2/day or so in terms of the water vapor permeability.
However, the substrate for use in organic EL devices is required to have a water vapor barrier capability on a higher level. As a means for satisfying the requirement, reported are a technique of employing an organic/inorganic barrier laminate produced by laminating an organic layer and an inorganic layer, thereby realizing a water vapor permeability of less than 0.1 g/m2/day (e.g., see JP-A 2003-335880 and JP-A 2003-335820), and a technique of realizing a more excellent water vapor barrier capability on a level of less than 0.01 g/m2/day in terms of water vapor permeability (see U.S. Pat. No. 6,413,645).
However, the organic/inorganic laminate barrier film substrates disclosed in these are problematic in that the organic layer therein is formed under an oxygen-free condition such as in vacuum or in a nitrogen stream atmosphere, therefore requiring additional equipment, long time and high cost; and the simplification of the film-forming step is a significant theme to be attained in the barrier laminate production.